I have mostly had adequate managers. I had one manager who may have had some potential at one point, but his manager was a bully, and he didn't have the strength to withstand it. His life was not easy.
I had a director who was excellent- he chaired a mediation meeting and every now and then would stop and say, let me summarise these points, to make sure I've understood them properly. If other people chaired meetings like him, they would be so much more efficient and productive.
I left my last job after 5 months because of micromanagement- he'd not managed anyone before, and I think if he had decent training, he might turn out all right, but it's a start-up and I don't think he'll get it there.
Current manager (10 months in) seems good. I almost cried in my mid-year review, because she didn't want to put me down all the time and is actually interested in my next career steps. Never really had that from a line manager before.
The trouble is, in many areas, people get promoted on their technical ability, and then the next step is people management, regardless of whether they've actually any skills in that - I'm in IT, and everyone grumbles about having yo fo "soft skills training" - usually they're not soft at all. Managing all those different personalities and ambitions (and lack of ambition) and abilities, personality clashes, etc, etc, none of thst is easy.
I remember someone at Dad's funeral saying he had seen Dad at work with some of the more challenging farm workers personslity-wise, and said because of seeing that, Dad was the sort of manager he aspired to be.